Cooling arrangement for a vacuum cleaner motor or the like



g- 1966 R. G. KROKER ETAL 3263,90

COOLING ARRANGEMENT FOR A VACUUM CLEANER MOTOR OR THE LIKE Filed May 15, 1964 a Sheets-Sheet 1 INVENTORS 1966 R. G. KROKER ETAL. 3,263,908

COOLING ARRANGEMENT FOR VACUUM CLEANER MOTOR OR THE LIKE Filed May 15, 1964 2 Sheets' sheet 2 INVENTORS.

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' ardZQfimrz miller United States Patent 3,263,908 COOLING ARRANGEMENT FOR A VACUUM CLEANER MOTOR OR THE LIKE Raymond G. Kroker, Normal, and Richard E. Kronmiller, Heyworth, Ill., assignors to National Union Electric Corporation, Stamford, Conn., a corporation of Delaware Filed May 15, 1964, Ser. No. 367,672 11 Claims. (Cl. 230-117) This invention relates to an improved motor-fan unit and more particularly to a novel and improved cooling arrangement for the motor of such a unit. Motor-fan units of the type here involved are particularly useful in vacuum cleaners, but may also be used in many other environments.

Because of the fact that the currently popular upright, lightweight-type vacuum cleaners employ a compact or slim line styling, the motor-fan unit of such cleaners must be small. Since most of the cleaners of this type depend solely upon suction for their cleaning action, the fan must operate at high speeds in order to develop the required vacuum. As a result of such high speed operation, a substantial amount of heat is developed by the motor of the unit which must be dissipated if permature failure is to be avoided. Such heat is also detrimental Where a plastic cleaner housing is employed in that excessive heat may cause the housing to become deformed or melt.

The heat dissipation problem is particularly aggravated in the aforementioned type of cleaner in that it is undesirable to utilize the main air flow through the cleaner for cooling the motor due to the back pressure that is developed and the consequent reduction in the suction available for cleaning.

Accordingly, it is a general object of the present invention to provide a novel andimproved motor-fan unit adapted for use in a variety of applications involving movement or flow of a gaseous fluid.

A more particular object is to provide a novel and improved cooling arrangement for the drive motor of a motor-fan unit of the foregoing character.

Another object is to provide a novel and improved cooling arrangement for the drive motor of an upright, lightweight type vacuum cleaner wherein a separate flow of cooling air from the exterior of the cleaner is utilized to cool the motor.

Still another object is to provide a novel and improved cooling arrangement of the foregoing character wherein the separate cooling air flow does not enter the casing which encloses the main suction fan.

A further object is to provide a novel cooling air flow arrangement for the fan drive motor of an upright, lightweight-type vacuum cleaner wherein the main air flow through the cleaner is utilized in a novel manner to augment a separate cooling air fiow through the motor casing.

Another object is to provide a novel combination cooling air flow augmenting means and a fan guard adapted for use with the motor-fan unit of a vacuum cleaner of the character described.

Still another object is to provide a novel combination cooling air flow augmenting means and'fan guard of the foregoing character which acts as a heat sink to cool at least one of the motor bearings of the motor-fan unit.

A further object is to provide a novel combination'cooling air flow augmenting means and fan guard 'of the foregoing character, which is simple in construction and economical to manufacture.

Other objects and advantages of the invention will become apparent from the following detailed description and accompanying sheets of drawings, in which:

FIG. 1 is a perspective view of a vacuum cleaner embodying the features of the present invention;

i the motor casing.

FIG. 2 is an enlarged, broken, longitudinal sectional view with some parts in elevation, taken substantially along the line 2--2 of FIG. 1;

- FIG. 3 is an end view of the upper end of the housing of the vacuum cleaner shown in FIGS. 1 and 2, taken substantially along the line 33 of FIG. 2;

FIG. 4 is an enlarged fragmentary longitudinal sectional view of the upper portion of the vacuum cleaner illustrated in FIG. 2 and showing additional structural details of the air flow arrangement therethrough;

FIG. 5 is a transverse sectional view taken substantially along the line 55 of FIG. 4; and

FIG. 6 is a fragmentary side elevational view of the fan motor casing of the cleaner taken substantially along the line 6-6 of FIG. 5, and showing additional details of the air flow directing structure.

Briefly described, the present invention contemplates an improved motor-fan unit for effecting movement or flow of a gaseous fluid, the unit incorporating a novel cooling arrangement for the fan drive motor thereof. While the motor-fan unit of the present invention may be used in a variety of applications, the structural details and operation thereof will be described hereinafter in conjunction with one specific application, namely as the means for producing a main or cleaning air flow through an upright, lightweight-type vacuum cleaner. Thus, the motor-fan unit generally comprises a motor portion and a fan portion, the motor portion including a motor which is enclosed in a casing and which serves to drive a main fan. The main fan is also enclosed in a casing secured to the motor casing. The motor and fan, together, com prise the aforementioned motor-fan unit or assembly which is mounted in and enclosed by the cleaner housing. The main fan provides a main or cleaning air flow through the cleaner housing which serves to draw dirt or other foreign particles into the housing through a flow pipe having a suitable attachment connected to the inlet end thereof. The dirt laden air passes through a suitable filter or bag within the housing, and substantially clean air from the filter is exhausted through outlet openings in the side Wall of the housing adjacent the motor portion of the motor-fan unit.

Because of the fact that the main air flow may contain minute particles of dirt, or moisture due to a wet pick-up situation or-possibly a broken filter bag, and may be at an elevated temperature due to its passage through the main fan, this air is not well suited for cooling the motor.

Instead, a novel-separate cooling air flow for. the motor is contemplated, such flow being substantially isolated from the main or cleaning .air flow. Such cooling air flow, to be-hereinafter described in detail, is provided inpart by a supplemental cooling fan secured to the drive shaft of the motor and-disposed within the motor casing. In addition, a novel flow directing means is provided for augmenting both the main and cooling air flows through Such flow directing means, in the embodiment of the invention described more fully hereinafter, comprises a plurality of circumferentially spaced radially outwardly extending blades or vanes disposed in the main air flow discharging from the main fan. The blades serve to augment the main air flow by reducing turbulence in the main fan casing and main air flow. The blades also serve to augment the cooling air flow by directing the main air flow across a plurality of openings or slots in the side wall of the motor casing, adjacent its lower end, to provide a venturi effect. Such venturi effect increases the cooling air flow through the motor casing. Preferably, the blades are inclined so as to lie in planes paralleling the natural flow path of the main air flow. A more uniform flow of the main air is thus obtained across the slots in the motor casing which contributes to the aforementioned venturi effect.

In addition to directing the main air flow across the slots in the motor casing, such blades also function as a guard for the main fan of the motor-fan unit as required by certain safety specifications for this type of device.

In FIG. 1, a vacuum cleaner incorporating a motorfan unit 26 shown in detail in FIGS. 2 and 4 and embodying the features of the present invention, is illustrated. The vacuum cleaner 10, in the present instance, comprises an elongated, separable housing 11 which includes a lower section 12 and an upper section 13. A pair of toggle clamps or latches 14, only one of which is shown in FIG. 1, are provided for holding the sections 12 and 13 engaged.

An intake or suction pipe 16 (FIGS. 1 and 2) is mounted within the lower casing section 12 and the upper end, indicated at 17, of the pipe terminates adjacent the upper end of the casing section 12. A U-shaped fitting or elbow 18 engages the upper end 17 of the pipe 16 and connects the latter with an elongated filter bag 19 removably secured to the other end of the elbow 18, as by a garter spring 15. The bag 19 is conventional to the extent that it is of porous paper, or similar materials, and is adapted to expand when subjected to a differential pressure. The pipe 16 extends through the lower end wall, indicated at 20, of the lower housing section 12, and a seal 21 (FIG. 2) is disposed between the pipe 16 and an opening in the end wall to provide an airtight joint therebetween. The lower end of the pipe 16 is adapted to receive various types of cleaning attachments, a rug and floor cleaner attachment 22 being illustrated.

A suitable handle 23 is secured to the upper housing section 13 to permit manipulation of the cleaner and lead wires 24 are provided for supplying current to the motor portion of the motor-fan unit 26 (FIG. 2) mounted within the upper casing section 13. A switch 27 controls current flow to the motor-fan unit 26 and the operation of the cleaner.

Referring now to FIG. 4 in conjunction with FIG. 2,

it will be seen that the motor-fan unit 26 includes a motor portion 28 enclosed by a generally cylindrical casing 29 and a depending fan portion 30 also enclosed by a generally cup-shaped casing 31 secured to the motor casing 29. The upper end of the motor casing 29 is engaged and centered in the housing section 13 by a support and seal ring 32 which is preferably of sponge rubber and which engages the end edges of a plurality of longitudinally extending circumferentially spaced ribs 33 in the upper end of the housing section 13. Another support and seal ring 34, also of sponge rubber, engages and centers the lower end of the fan casing 31, the ring 34 being retained by a mounting ring 35 which engages the inner wall of the housing section 13.

The motor casing 29 of the unit 26, in the present instance, comprises a two-piece casing which includes an upper inverted cup-shaped section 36 and a lower cupshaped section 37. A pair ofradia'lly outwardly extending flanges 38 are provided around the adjacent end edges of the motor casing sections 36 and 37 for receiving screws 39, or the like, which hold the sections together.

Mounted within the motor casing sections is an electric motor 44 which, in the present instance, comprises a field coil assembly defined by a stack of laminations 46 and an armature assembly 47 which is mounted on a shaft 48. The laminations 46 are supported and located in the motor casing 29 by indentations or lances (not shown) in the annular side wall portions, indicated at 49, of the motor casing sections 36 and 37. Such indentations engage the uppermost and innermost laminations of the stack 46 when the screws 39 are drawn up. To permit this, the annular side wall portions 49 have an axial length, such that when the casing sections 36 and 37 are drawn together by the screws 39 with the indentations engaging the laminations 46, a gap 50 is defined between the flanges 38.

The armature shaft 48 is rotatably carried in bearing assemblies 51 and 52 mounted in the upper and lower end walls, indicated at 53 and 54, respectively, of the motor casing sections 36 and 37. Current is supplied to the armature 47 by a commutator 55 and brushes 56, the latter being carried in a brush holder assembly 57. The assembly 57 is supported by a pair of screws 58, only one of which is shown in FIG. 4, which extend through the laminations 46. The brushes 56 are connected by wires 59 to the electrical lead wires 24 and switch 27 (FIG. 2).

The fan portion 30 of the unit 26, in the present instance, comprises a two-stage centrifugal-type fan 61 which includes a pair of axially spaced rotating elements 62 and 63 and a fixed or stator element 64 disposed between the rotating elements 62 and 63. The rotating elements 62 and 63 are mounted on a hub 65 at the lower end, indicated at 66, of the motor shaft 48 and are secured thereto by a nut 67. The stator element 64 serves to redirect the flow of air from the element 62 into the element 63 when the fan 61 is being driven.

The rotating fan elements 62 and 63, as well as the stationary fan element 64, are provided with a plurality of generally radially extending arcuate blades 72 (FIGS. 4 and 5) which are carried between axially spaced disks 73. The upper disk of the stator element 64 is formed by the end wall, indicated at 74, of a shallow cup-shaped casing section 75 which nests in the upper end of a larger cup-shaped casing section 76. The end wall of the casing section 76 has a central opening '77 therein forming an inlet for the fan portion 30, such inlet being covered by a sheet metal guard '78 carried by the mounting ring 35 and having openings therein. The upper and lower casing sections 75 and 76 thus comprise the fan casing 31.

In the present instance, the lower casing section 76 is secured to the upper casing section 75 by a press fit and further retained by interlocking dimples 79. The upper fan casing section 75 is secured to the lower motor casing section 37 by a plurality of machine screws 80 (FIG. 2) which extend through upwardly extending tabs or lugs 81 on the upper casing section 75. The screws 80 are threaded into internally threaded tubular extrusions 82 (FIGS. 4 and 5) formed in the side wall portion 49 of the motor casing section 37.

As will be apparent from FIG. 4, the diameter of the rotating fan elements 62, 63 and stator 64 is somewhat less than the internal diameter of the fan casing 31, and a substantially annular opening for air discharging upwardly from the periphery of the fan element 63 is defined between the annular side wall, indicated at 83, of the upper fan casing section 75 and the lower end of the motor casing 29, particularly the annular side wall 49 of the casing section 37. Such opening communicates with an outlet in the upper housing section 13, for discharge to the atmosphere. Such outlet, in the present instance, comprises a plurality of longitudinally extending circumferentially spaced slots 84 (FIGS. 1, 3 and 4). A plurality of circumferentially spaced longitudinally extending ribs 86 (FIGS. 2 and 4) are provided on the inner side wall of the upper housing section 13 to strengthen the latter in the area of the slots 84.

With the foregoing construction, it will be apparent that upon closing of the switch 27 and energization of the motor 44, the fan 61 will rotate thereby providing suction at the fan inlet 77 and a reduction in pressure in the interior of the lower housing section 12 and around the filter bag 19. The fan 61 thus provides a main or cleaning air flow through the cleaner 10, the flow originating at the attachment 22 and proceeding upwardly through the pipe 16 to the filter bag 19, through the latter to the interior of the housing section 12, and thence through the fan portion 30 to the interior of the upper housing section 13 from whence it discharges through the slots 84 to the atmosphere. Dirt and other foreign particles are trapped in the filter bag 19 so that substantially clean air passes through the fan portion 30 for discharge through the outlet slots 84.

Such main air flow thus exerts some cooling effect on the motor as it flows around the motor casing sections 36 and 37 toward the outlet slots 84. However, this main air flow is not suitable for cooling the motor 44 by directing it through the interior of the motor casing 29 because such a flow would substantially increase the back pressure on the main air flow and thus reduce the suction available for cleaning. In addition, the mean air flow may contain minute particles of dirt, or may contain moisture due to a wet pick-up situation or possibly a broken filter bag. Either condition is injurious to the motor 44.

To this end, a motor cooling fan 90 (FIG. 4) having a plurality of blades 91 therearound is mounted on the motor shaft 48 within the upper motor casing section 36 and adjacent the upper end wall 53 thereof. The fan 90 is adapted to supply a cooling air flow to the interior of the motor casing 29, which is wholly separate from the main air flow provided by the fan 61. To provide for such separate cooling air flow, the upper end wall 53 of the motor casing section 36 is provided with a plurality of openings 92 therethrough, the latter communicating with a plurality of radially extending circumferentially spaced slots 93 (FIGS. 3 and 4) formed in the upper end of the housing section 13.

Thus, when the motor 44 is operating to provide the main air flow through the housing 11, the fan 90 will also supply a separate cooling air flow to the interior of the motor casing 29 to cool the motor 44. Such cooling air flow passes around and through the components of the motor 44 and then discharges into the interior of the upper housing section 13 through a plurality of circumferentially extending openings or slots 94 (FIGS. 2 and 4) in the side Wall 49 of the lower motor casing section 37 immediately above the end wall 54 thereof. A portion of the cooling air flow will discharge radially outwardly through the gap 50 to the interior of the housing section 13 and thence through the outlet slots 84. The cooling air flow thus does not become mixed with the main air flow discharging upwardly from the fan 61 until the former leaves the motor casing 29. The possibility of damage to the motor 44 from minute particles of dirt or moisture which may be present in the main air flow from the fan due to a broken filter bag or a wet pick-up situation, is thus eliminated.

The location of the slots 94 in the lower portion of the motor casing side wall 49, rather than in the end wall 54, provides a significant structural advantage in that the end wall 54 does not have to be weakened by cutouts or openings to accommodate a cooling air flow. In addition, the absence of large openings in the end wall 54' permits the latter to conduct heat away from the lower bearing 52 for dissipation in the main air flow, as will be described more fully hereinafter.

Because of the fact that the main air flow' in the interior and at the outlet of the fan casing 31 is turbulent, it is desirable to reduce such turbulence in order to reduce flow losses and increase the suction of the cleaner. To this end, stator means in the form of a plate-like member or disk 1.01 having a plurality of circumferentially spaced radially outwardly extending flow straightening blades or vanes 102 therearound, is provided.

The disk 101, in the present instance, is preferably formed from sheet metal and secured to the end wall 54 by extruding or otherwise forming the material of the disk 101 to provide a plurality of axially upwardly extending tubular portions or extrusions 103 which are adapted to extend tliroug'h openings in the end wall 54. The inner ends of the tubular portions 103 are flared as at 104 to rigidly connect the disk 101 to the end wall 54.- The combined area of the open central portions of the tubular portions 103 is so small that no significant air flow will occur therethrough. The main and cooling air 6 flows thus remain separated throughout their passage through the motor-fan unit 26.

The blades 102 are divided into four circumferentially spaced groups of four blades each and span the annular discharge opening for the fan 61. Such opening is de fined by the space between the inner wall 83 of the fan casing section 75 and the motor casing side wall 49. The groups of blades are circumferentially spaced to accommodate the upwardly extending lugs or tabs 81 (FIGS. 2 and 5) of the fan casing 31.

The blades 102 are preferably inclined with respect to the axis of rotation of the fan 61 so as to lie in planes parallel to the natural flow path of the main air flow discharging upwardly from the fan 61 and out of the fan casing 31. A blade angle of from about 15 to about 55 will be preferred, dependent upon such factors as motor speed and fan diameter. The use of a blade angle within this range results in a significant increase in the efiiciency of the fan system. For example, in the embodiment shown in the drawing having a motor speed of about 16,500 r.p.m. and a fan diameter of about 3% inches, a blade angle of about 45 is used and results in about a 10% increase in air flow.

The aforementioned upward flow of air across the slots 94 provides another advantage in that because of the high velocity of the main air flow, a venturi effect is achieved at the slots 94. Such venturi effect provides a substantial increase in the flow of cooling air through the motor casing 29 than could be achieved from a utilization of the low pressure zone in the fan casing 30, between the bearing 52 and upper fan element 53, for this purpose.

In addition to increasing the suction developed by the motor-fan unit 26, the disk 101 and blades 102 also function as a heat sink for cooling the lower motor bearing assembly 52. Thus, heat from the bearing 52 flows through an annular axially extending flange 106 in which the bearing 52 is mounted and then flows radially outwardly through the end wall 54 and disk 101 to theiblades 102. After reaching the blades 102, the heat is carried off in the main air flow. Because of the number of blades 102 around the periphery of the disk 101, a substantial quantity of heat can be dissipated in the main air flow passing between the blades.

A similar heat sink effect is achieved by the fan with respect to the upper bearing assembly 51. In this instance, heat from the bearing 51 flows through the shaft 48 to the hub of the fan 90 and thence radially outwardly to the blades 91 where it is carried off in the cooling air flow entering the motor casing 29,isuch air being.

substantially-at room temperature and not being subjected to the heating effect of passage through the mo tor 44.

The blades 102 also serve another purpose in that because they extend across and substantially cover the. arinular discharge outlet at the upper end of the fan casing 31 they function-as a guard. As such, the blades 102 -satisfy certain specifications covering fan devices, as previously mentioned.

Because of the fact that the disk 101 and blades 102 are preferably of sheet metal, they may be readily formed in one piece by a stamping operation which construction is simple and low in cost.

The motor cooling arrangement heretofore described is eflfective to prevent over-heating or burn-out of the motor 44 during periods of operation when themain air flow through the unit 26 is low or completely stopped, such as would occur if the attachment 22 became obstructed or the filter bag 19 became clogged. Thus, should either of these conditions occur, the speed of the motor 44 and fan 61 would increase due to unloading of the latter thereby providing more cooling air through the motor. While the motor would draw less current at this time, a sufiicient amount of heat would still be generated to cause damage or even failure of the motor unless adequately cooled. Cooling under such an operating condition is achieved by the fan 90 which provides a cooling air flow through the motor casing 29 Wholly independent of the main air flow. Damage to the motor is thus avoided.

When the attachment 22 is not in contact with a surface to be cleaned, or the intake pipe 16 and filter bag 19 are unobstructed, the fan 61 will deliver the greatest fiow of air and the motor will draw maximum wattage. At this time, the speed of the motor 44 and fan 61 will drop, but adequate cooling of the motor 44 is assured by the flow of cooling air through the motor casing 29, such flow being due to the fan 90 as augmented by the venturi action of the main air flow across the slots 94.

As peviously mentioned, while the motor-fan unit 26 has. been described herein in conjunction with the vacuum cleaner 10, such unit is also useable in other applications involving the movement or flow of a gas. Thus, the motor-fan unit 26 could also be used, for example, to exhaust gases from a fume hood, as a cooling fan for exhausting hot air from the interior of a housing enclosing a business machine or the like, or merely as a suction generating device. The novel motor cooling arrangement of the unit 26 renders it particularly well suited for use in the first two exemplary applications due to the fact that a separate flow of cooling air, wholly independent of the main flow through the unit, may be employed to cool the motor 44. Thus, even though the main fluid flow through the unit 26 may be poorly suited or incapable of use for cooling the motor 44, the separate cooling fluid flow through the motor casing 29 permits operation of the unit 26 in such an environment.

While only one embodiment of the invention has been herein illustrated and described, it will be understood that modifications and variations thereof may be effected without departing from the scope of the invention as set forth in the appended claims.

We claim:

1. A motor-fan unit comprising a motor portion and a fan portion, said motor portion including a generally cylindrical casing having an annular side wall, an end wall and a motor mounted therein, said fan portion including a generally cup-shaped casing having an annular side wall of greater diameter than said motor casing side wall and an end wall having a main air inlet therein, said fan casing being secured to one end of said motor casing so that theopen end of said fan casing and said one end of said motor casing define an annular axially opening main air outlet for said fan portion adjacent said motor casing end wall, said outlet being unobstructed downstream therefrom, a fan in said fan casing connected to said motor and operable when driven to provide a main air flow through said fan portion, and a combined fan guard and stator means including a plurality of inclined blades disposed in said main air outlet of said fan portion for increasing the flow of air therethrough, said blades spanning said outlet and also serving as a guard for said fan.

2. A motor-fan unit comprising a motor portion and a fan portion, said motor portion including a generally cylindrical casing having an annular side wall, an end wall, and a motor mounted therein, said fan portion including a generally cup-shaped casing having an annular side wall of greater diameter than said motor casing side wall and an end wall having a main air inlet therein, said fan casing being secured to one end of said motor casing so that the open end of said fan casing and said one end of said motor casing define an annular main air outlet for said fan portion adjacent said motor casing end wall, a fan in said fan casing connected to said motor and operable when driven to provide a main air flow through said fan portion, and stator means secured to said motor casing end wall and having a plurality of annularly arranged blades spanning said annular main air outlet of said fan portion, said blades being inclined with respect to the axis of rotation of said fan so as to lie in planes parallel to the natural flow path of air discharging from said fan, whereby said blades are effective to increase the flow of suction air through said fan portion, said blades also serving as a guard for said'fan.

3. The combination of claim 2 further characterized in that said blades have an angle of inclination of between about 15 and 55.

4. The combination of claim 2 further characterized in that said stator means comprises a sheet metal disk having a plurality of integral radially outwardly extending blades around the periphery thereof.

5. The combination of claim 4 further characterized in that said disk includes a plurality of integrally formed tubular portions extending upwardly through openings in said motor casing end wall, the ends of said tubular portions being flared to secure said disk to said end wall.

6. A motor-fan unit. comprising a motor portion and a fan portion, said motor portion including a generally cylindrical casing having an annular side wall, spaced end walls, and a motor mounted therein, said fan portion including a generally cup-shaped casing having an annular side wall of greater diameter than said motor casing side wall and an end wall having a main air inlet therein, said fan casing being secured to one end of said motor casing so that the open end of said fan casing and said one end of said motor casing define an annular main air outlet for said tan portion, a fan in said fan casing connected to said motor and operable when driven to provide a main air flow through said fan portion, said main air outlet discharging air across at least a portion of the annular side wall of said motor casing, said motor casing also having a cooling air inlet in the other end wall thereof, and means coacting with said main air flow for inducing a cooling air fiow through said motor casing, said coacting means comprising at least one opening in the side wall of said motor casing registering with a high velocity zone of said main air flow, whereby a separate flow of cooling air is induced through said motor casing to cool said motor.

7. The combination of claim 6 further characterized in that said opening in said motor casing side wall comprises a plurality of circumferentially spaced slots.

8. The combination of claim 7 further characterized in that said slots are disposed closely adjacent said one end wall of said motor casing and said annular main air outlet.

9. The combination of claim 6 further characterized in that a cooling fan is provided in said motor casing and driven by said motor, said cooling air fan providing a flow of cooling air through said motor casing in addition to the flow induced therethrough by said main air flow.

10. A motor-fan unit comprising a motor portion and a fan portion, said motor portion including a generally cylindrical casing having an annular side wall, spaced end walls, and a motor mounted therein, said fan portion including a generally cup-shaped casing having an annular side wall of greater diameter than said motor casing side wall and an end wall having a main air inlet therein, said fan casing being secured to one end of said motor casing so that the open end of said fan casing and said one end of said motor casing define an annular main air outlet for said fan portion, a fan in said fan casing connected to said motor and operable when driven to provide a main air flow through said fan portion, said main air outlet discharging air across at least a portion of the annular side wall thereof of said motor casing, said motor casing also having a cooling air inlet in the other end wall thereof, and means coacting with said main air flow for inducing a cooling air flow through said motor casing, said coacting means comprising at least one opening in the side wall of said motor casing registering with a. high velocity zone of said main air flow, and stator means including a plurality of inclined blades disposed in said main air outlet for increasing the main air flow through said fan portion and across said opening, said increased main air flow across said opening increasing the flow of cooling air through said motor casing.

11. A motor-fan unit comprising a motor portion and a fan portion, said motor portion including a generally cylindrical casing having an annular side Wall and spaced end walls, bearing means carried by each of said end walls, a motor Within said casing having a shaft rotatably journalled in said bearing means, said fan portion including a generally cup-shaped casing having an annular side wall and an end wall having a main air inlet therein, said fan casing being secured to said motor casing with the open end of said fan casing disposed adjacent one end wall of said motor casing so as to define an annular main air outlet for said fan portion, a fan in said fan casing secured to said motor shaft and operable when driven to provide a main air flow through References Cited by the Examiner UNITED STATES PATENTS 2,333,017 10/1943 Leathers 2301 17 2,534,808 12/1950 Bevington et a1. 230-117 2,726,807 12/1955 Lewis 230--130 2,778,563 1/1957 Doyle 230-1 17 2,822,122 2/1958 Cole 230-117 3,171,353 3/1965 McMahan 230-130 X 20 ROBERT M. WALKER, Primary Examiner. 

1. A MOTOR-FAN UNIT COMPRISING A MOTOR PORTION AND A FAN PORTION, SAID MOTOR PORTION INCLUDING A GENERALLY CYLINDRICAL CASING HAVING AN ANNULAR SIDE WALL, AN END WALL AND A MOTOR MOUNTED THEREIN, SAID FAN PORTION IN CLUDING A GENERALLY CUP-SHAPED CASING HAVING AN ANNULAR SIDE WALL OF GREATER DIAMETER THAN SAID MOTOR CASING SIDE WALL AND AN END WALL HAVING A MAIN AIR INLET THEREIN, SAID FAN CASING BEING SECURED TO ONE END OF SAID MOTOR CASING SO THAT THE OPEN END OF SAID FAN CASING AND SAID ONE END OF SAID MOTOR CASING DEFINE AN ANNULAR AXIALLY OPENING MAIN AIR OUTLET FOR SAID FAN PORTION ADJACENT SAID MOTOR CASING END WALL, SAID OUTLET BEING UNOBSTRUCTED DOWNSTREAM THEREFROM, A FAN IN SAID FAN CASING CONNECTED TO SAID MOTOR AND OPERABLE WHEN DRIVEN 